In recent years, the technical trend of automobile industry has been focused on developments of digitalizing each system for the purpose of driver's convenience over the previous mechanical aspect such as an engine
In detail, as one example of digitalizing an automobile, there is a technique on a vehicle rain sensor for automatically controlling a vehicle wiper according to an amount of rainfall. Even though a driver does not manually operate a wiper during raining, such a rain sensor senses an amount of rainfall to automatically control the operation of the wiper, so that the driver's convenience may be improved.
As one example of the vehicle rain sensor, there is an optical rain sensor in which a light emitting unit and the light receiving unit are installed at an inside of the front glass of a vehicle and an amount of rainfall is determined by using an variation of intensity of light received by the light receiving unit due to the variation of a light refractive index by rain drops. However, according to the optical rain sensor of the related art, since the structure and the installation are complex and the components are expensive, the producing cost is increased. In addition, the measuring area is small and influenced by various kinds of contaminants, so that the accuracy may be degraded.
In addition, as another example, there is a vehicle rain sensor of determining whether it is raining and an amount of rain drops by measuring the wire impedance varied with the raindrop on a wire disposed inside the windshield glass of a vehicle. However, in case of the vehicle rain sensor, the wire is viewed so that the driver's sight may be disturbed, so that the size and position may be limited.
Meanwhile, since a mist on a vehicle windshield glass is an interrupting element of driving, a driver must operate an air conditioner or a hot-wire during driving to remove the mist from the surface of a vehicle windshield glass, so that the driver's concentration on driving may be disturbed.